﻿// Copyright (c) 2011 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Xml;
using System.Xml.Linq;

namespace ICSharpCode.ILSpy
{
    /// <summary>
    /// Manages IL Spy settings.
    /// </summary>
    public class ILSpySettings
    {
        readonly XElement root;

        ILSpySettings()
        {
            this.root = new XElement("ILSpy");
        }

        ILSpySettings(XElement root)
        {
            this.root = root;
        }

        public XElement this[XName section]
        {
            get
            {
                return root.Element(section) ?? new XElement(section);
            }
        }

        /// <summary>
        /// Loads the settings file from disk.
        /// </summary>
        /// <returns>
        /// An instance used to access the loaded settings.
        /// </returns>
        public static ILSpySettings Load()
        {
            using (new MutexProtector(ConfigFileMutex))
            {
                try
                {
                    XDocument doc = LoadWithoutCheckingCharacters(GetConfigFile());
                    return new ILSpySettings(doc.Root);
                }
                catch (IOException)
                {
                    return new ILSpySettings();
                }
                catch (XmlException)
                {
                    return new ILSpySettings();
                }
            }
        }

        static XDocument LoadWithoutCheckingCharacters(string fileName)
        {
            // XDocument.Load(fileName) validates that no invalid characters appear (not even in escaped form),
            // but we need those characters for some obfuscated assemblies.
            using (XmlTextReader r = new XmlTextReader(fileName))
            {
                return XDocument.Load(r);
            }
        }

        /// <summary>
        /// Saves a setting section.
        /// </summary>
        public static void SaveSettings(XElement section)
        {
            Update(
                delegate(XElement root)
                {
                    XElement existingElement = root.Element(section.Name);
                    if (existingElement != null)
                        existingElement.ReplaceWith(section);
                    else
                        root.Add(section);
                });
        }

        /// <summary>
        /// Updates the saved settings.
        /// We always reload the file on updates to ensure we aren't overwriting unrelated changes performed
        /// by another ILSpy instance.
        /// </summary>
        public static void Update(Action<XElement> action)
        {
            using (new MutexProtector(ConfigFileMutex))
            {
                string config = GetConfigFile();
                XDocument doc;
                try
                {
                    doc = LoadWithoutCheckingCharacters(config);
                }
                catch (IOException)
                {
                    // ensure the directory exists
                    Directory.CreateDirectory(Path.GetDirectoryName(config));
                    doc = new XDocument(new XElement("ILSpy"));
                }
                catch (XmlException)
                {
                    doc = new XDocument(new XElement("ILSpy"));
                }
                doc.Root.SetAttributeValue("version", RevisionClass.Major + "." + RevisionClass.Minor + "." + RevisionClass.Build + "." + RevisionClass.Revision);
                action(doc.Root);
                // We can't use XDocument.Save(filename) because that checks for invalid characters, but those can appear
                // in obfuscated assemblies.
                using (XmlTextWriter writer = new XmlTextWriter(config, Encoding.UTF8))
                {
                    writer.Formatting = Formatting.Indented;
                    doc.Save(writer);
                }
            }
        }

        static string GetConfigFile()
        {
            return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "ICSharpCode\\ILSpy.xml");
        }

        const string ConfigFileMutex = "01A91708-49D1-410D-B8EB-4DE2662B3971";

        /// <summary>
        /// Helper class for serializing access to the config file when multiple ILSpy instances are running.
        /// </summary>
        sealed class MutexProtector : IDisposable
        {
            Mutex mutex;

            public MutexProtector(string name)
            {
                bool createdNew;
                this.mutex = new Mutex(true, name, out createdNew);
                if (!createdNew)
                {
                    try
                    {
                        mutex.WaitOne();
                    }
                    catch (AbandonedMutexException)
                    {
                    }
                }
            }

            public void Dispose()
            {
                mutex.ReleaseMutex();
                mutex.Dispose();
            }
        }
    }
}
